1. Field of the Invention
This invention relates to gas turbine engine parameter sensors and more particularly to the design and construction of a magnetic device for converting the parallel output of a digital parameter sensor into serial form for transmission to a control unit.
2. Description of the Prior Art
As gas turbine engine control systems have become more sophisticated the tendency has been utilize more digital computers and digital controls. A natural outgrowth of the trend towards digital control systems has been the development of direct digital engine parameter sensors to replace the traditional analog sensors the output of which required conversion to digital signals prior to bein useful to a digital control system. Typical of these direct digital sensors is a magnetic shaft encoder which provides a digital indication of the angle of a shaft by saturating or unsaturating a number of encoder magnetic cores.
While such direct digital engine parameter sensors represent a tremendous advancement in the field of gas turbine engine controls, they do present one major problem. Due to their inherent operational nature, their output is presented in parallel form. Thus, in order to obtain accurate parameter information it is necessary to have an individual conductor for each bit of information sensed. For example, a magnetic shaft encoder capable of position sensing with eight-bit accuracy would require nine conductors running between the sensor and the engine control unit (one for sending an excitation current to the magnet shaft encoder and one for sending each of the eight bits of information back to the engine control unit).
While a few additional conductors may not be particularly important with respect to an individual sensor, as gas turbine engine control systems have become more sophisticated, the number of such sensors has increased and the multiplicity of such conductors has become highly significant in terms of space and weight complications.
It therefore became highly desirable to convert the parallel output of direct digital engine parameter sensors into serial form for transmission to the engine control unit over a single conductor. However, because of the temperature extremes (-65.degree. F. to 400.degree. F.) involved with remotely located engine parameter sensors, the use of conventional electronic parallel-to-serial-conversion techniques was found to be impractical. The problem of converting parallel digital information to serial form at remote engine sensor locations without the use of conventional electronics is overcome by the present invention.
An object of the present invention is to provide a magnetic parallel-to-serial converter for use at remote sensor locations which will significantly reduce the number of conductors between the remote sensor and the engine control unit.
A further object of the present invention is to provide a magnetic parallel-to-serial converter which will operate effectively over a widely varying temperature range.